1. Technical Field of the Invention
The present invention relates to a spray-drying device, comprising a vertical drying chamber which comprises: a material feed for supplying material which is to be spray-dried, an atomization means for atomizing the material which is to be spray-dried, a drying-gas feed for supplying drying gas, a drying-gas discharge for discharging drying gas, a material discharge for discharging spray-dried material, filter means for separating entrained fine particles out of discharged drying gas, and fine-particle removal means for removing fine particles which have been deposited on the filter means from the filter means.
2. Prior Art
WO 97/14288 has disclosed a spray-drying appliance having a vertically arranged drying chamber with an atomization device and means for introducing a flow of drying gas. Furthermore, a number of filter elements with substantially inflexible filter walls are arranged in the top part of the chamber, for retaining particles which are entrained with the drying gas. The filter elements are in communication with a compressed-gas feed which at intervals applies pulsed pressure to the filter elements so as to remove the particles which have been retained.
One drawback of this known device is that the particles which have been detached from the filter elements (also known as fines or fine particles) might become mixed with the unentrained, heavier spray-dried particles (also known as heavies) in the drying chamber. This entails the risk of a mixture of particles with different properties, including particle size distribution and moisture content, being formed.